to elaborate, the way you have it, as a binomial, would mean that each deer caught has a 6/30 chance of being tagged. but this is not the case. if you catch a deer and it is tagged, then there are 24 untagged deer and 5 tagged deer remaining. so on your next catch, you would a 5/29 chance of catching a tagged deer. but you can use a hypergeometric distribution on this to make it a little easier.